linux-kernel - Re: [PATCH 11/13] kexec-bzImage: Support for loading bzImage using 64bit entry

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Message-ID: <20140624182314.GA15068@pd.tnic>
Date:	Tue, 24 Jun 2014 20:23:14 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
	ebiederm@...ssion.com, hpa@...or.com, mjg59@...f.ucam.org,
	greg@...ah.com, jkosina@...e.cz, dyoung@...hat.com,
	chaowang@...hat.com, bhe@...hat.com, akpm@...ux-foundation.org,
	gong.chen@...ux.intel.com
Subject: Re: [PATCH 11/13] kexec-bzImage: Support for loading bzImage using
 64bit entry

On Tue, Jun 24, 2014 at 01:31:25PM -0400, Vivek Goyal wrote:
> I think problem is that we shift 1 by 32 bits in this case (31 - 0 +
> 1) and that overflows the size of unsigned. So there is this corner
> case where it does not seem to work (or atleast outputs warning).

Right, that is a corner case which overflows the shift. The only thing I
can think of right now is:

#define GENMASK(h, l)           ((u32)GENMASK_ULL(h, l))

u32 because we're implicitly assuming we're dealing with 32-bit unsigned
quantities.

There might be a better solution though...

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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